Nasal carriage of Staphylococcus aureus among patients receiving allergen-injection immunotherapy:: Associated factors and quantitative nasal cultures

OBJECTIVE: To compare the prevalence of nasal Staphylococcus aureus carriage among outpatients receiving allergen-injection immunotherapy with the prevalence among healthy controls and to determine predictors of nasal S aureus carriage. DESIGN: Survey. SETTING: Allergy clinic of a university hospital. PARTICIPANTS: A volunteer sample consisting of 45 outpatients undergoing desensitization therapy and 84 first- and second-year medical students. RESULTS: The nasal S aureus carriage rate was significantly higher among patients (46.7%) than among students (26.2%; P = .019). In a multivariate model adjusted for age and gender, the presence of atopic dermatitis or eczema was the only independent predictor of nasal S aureus carriage (odds ratio [OR], 4.4; 95% confidence interval [CI95], 1.2-16.0; P = .02). The only other participant characteristic associated with nasal S aureus carnage was immunotherapy with allergen injections (OR, 1.98; CI95, 0.7-6.0), but this association did not reach statistical significance (P = .23). The probability of nasal S aureus carriage was 88.9% for patients receiving allergen injections and having atopic dermatitis or eczema, and 36.1% for patients receiving allergen injections without atopic dermatitis or eczema. CONCLUSIONS: Patients undergoing desensitization have a higher nasal carriage rate of S aureus. However, factors other than the regular use of needles, and in particular abnormalities related to the atopic constitution of these patients, may predispose this population for S aureus carriage.